A pile of plant record labels, mysteriously stripped from accessioned plants in the Arboretum’s Rhododendron Dell, sent Manager of Plant Records Kyle Port on a mission to assess, verify, and relabel the collection.

In this issue, Kyle reports on the early history of Rhododendron Dell, and in the next issue he will write about the multi-layered curatorial process involved in the Rhododendron Dell project.

One hundred forty years ago, a triumphant rhododendron show bloomed on the Boston Common. For a nominal fee, attendees were ushered under tents where plants from private collections, including those of Arnold Arboretum director Charles S. Sargent and the event’s sponsor, H. H. Hunnewell, were arranged. Rhododendron hybrids imported from Anthony Waterer (Knap Hill Nursery, Woking, England) garnered considerable attention. The revelation that R. ‘Album Elegans’ and a few other cultivars were hardy outdoors in the Boston area soon fostered planting trials beyond conservatory walls, specifically in the burgeoning landscapes of the Arnold Arboretum, which had been established just the year before. More importantly, the friendships forged at the Boston show guaranteed that the most sought after rhododendron hybrids of the day would become accessible for viewing and study, free of charge, to anyone who journeyed to the Arboretum.

A black and white photo of the white flowered R. ‘Album Elegans’.
A color photo of Rhododendron Dell.
A black and white photo of the 1924 Loder Rhododendron Cup.

A suitable location for cultivating these large-leaved rhododendrons was found in a wind sheltered two-acre area between the northern contours of Hemlock Hill and Valley Road, through which Bussey Brook flows. Eventually named Rhododendron Dell, the existing soils—Hinckley sandy loam and Scio very fine sandy loam—proved adequate. Stands of eastern hemlock (Tsuga canadensis), intentionally left by the previous land owner Benjamin Bussey (1757–1842), provided an ideal amount of shade. And above all, the site allowed for cold air to sink away toward low-lying Bussey Brook Meadow.

The new hybrids were not immediately planted in Rhododendron Dell; instead, the first plantings on the site were of the hybrids’ North American parent species, which included R. catawbiense, R. maximum, and R. minus. It is likely that the only remaining plants from these early plantings exist in a mass planting of R. maximum accessions 23020 and 23021. These accessions actually comprise a number of accessions that were interplanted over the years and became indistinguishable from each other. The oldest of these R. maximum accessions was obtained as seeds in 1880 from Benjamin Marston Watson’s Old Colony Nurseries and Seed Warehouse in Plymouth, Massachusetts.

In 1886, the first R. catawbiense hybrids from Anthony Waterer were planted in Rhododendron Dell. Some of these hybrid cultivars had been featured in the tents of the 1873 rhododendron show on Boston Common, but now they were being planted outdoors to see how they would fare. Among these inaugural cultivars, R. ‘Purpureum Grandiflorum’ (accession 2804) and R. ‘Album Grandiflorum’ (accession 2805- A) survive to this day. Subsequent introductions such as R. ‘Mrs. Harry Ingersoll’ (accession 6202-C, acquired in 1891) epitomize the allure these hybrid rhododendrons had upon so many. Their survival at the Arboretum solidified a resolve to develop, evaluate, and maintain a collection for the ages. As Sargent wrote to Anthony Waterer in February 1911, “I think that we should have here a correctly named standard set of the hardy hybrid Rhododendrons as so many people depend on the Arboretum for information on such a subject.”

Citation: Port, K. 2013. Rediscovering Rhododendron Dell, part 1. Arnoldia, 70(4): 15–18.

While the majority of the early acquisitions of hybrids in Rhododendron Dell were those of Anthony Waterer and his cousin, John Waterer, a number of other international hybridizers are also represented. Fellow Englishman G. Paul provided R. ‘Duke of York’ (accession 22616-A, 1921 lineage from a 1915 introduction), and in 1908 German T. J. Rudolf Seidel sent, among others, R. ‘Echse I’ (accession 6175-B), which has bright reddish purple flowers with wavy-edged petals.

In 1919, the federal government’s passage of Quarantine No. 37 governing the importation of nursery stock halted shipments of plants by steamer directly to Boston. The Arboretum had a nearly exclusive reliance on overseas suppliers at the time, but this quarantine forced relationship-building closer to home. North American nurseries, hybridizers, and hobbyists stepped up to meet the challenge and became reliable allies in the development of the Rhododendron Dell collections.

A color photo of Rhododendron ‘Duke of York’.
Rhododendron ‘Duke of York’. Kyle Port

Kyle Port is Manager of Plant Records at the Arnold Arboretum.